1. Field of the Invention
The present invention relates to a curable polymer composition. More particularly, the present invention relates to a curable polymer composition comprising a curable alkyl (meth)acrylate, a curable oxyalkylene base polymer and two specific silicon-containing compounds, which composition has improved storage properties without deteriorating elongation of a cured material produced from said composition.
The term "alkyl (meth)acrylate" herein used is intended to mean an alkyl ester of acrylic acid and/or an alkyl ester of methacrylic acid.
2. Description of the Related Art
Polymers of alkyl (meth)acrylates having at least one silicon-containing group to the silicon atom of which a hydroxy group or a hydrolyzable group is bonded and which is cross linkable through formation of a siloxane bond (hereinafter referred to as a "silicon-containing reactive group") are disclosed in Japanese Patent Kokai Publication No. 36395/1979 and the like. Such polymers are cured by crosslinking the silicon-containing reactive group particularly with moisture in the air to provide a cured material having good weather resistance and water resistance.
Polymers comprising oxyalkylene units having the silicon-containing reactive group are disclosed in U.S. Pat. Nos. 3,971,751, 3,979,384 and 4,323,488 the disclosures of which are hereby incorporated by reference, Japanese Patent Publication Nos. 36319/1970, 12154/1971 and 32673/1974, and Japanese Patent Kokai Publication Nos. 156599/1975, 73561/1976, 6096/1979, 82123/1980, 123620/1980, 125121/1980, 131022/1980, 135135/1980 and 137129/1980. The oxyalkylene base polymers are also cured by crosslinking them at room temperature to provide an elastomeric cured material having good elongation properties.
The alkyl (meth)acrylate base polymers having the silicon-containing reactive group provide a fragile cured material. Even though they are prepared to have a low glass transition temperature, the cured material has deteriorated tensile properties such as a small tensile elongation and greatly decreased strength.
The oxyalkylene base polymers having the silicon-containing reactive group give cured material having good tensile properties although the cured material has insufficient weather resistance or poor adhesion to various substrates.
As above, neither the alkyl (meth)acrylate base polymer having the silicon-containing reactive group nor the oxyalkylene base polymer having the silicon-containing reactive group can provide the cured material with satisfactory properties. These defects of the two polymers are due to the structures of the backbone chains.
To improve the defects of the alkyl (meth)acrylate base polymer having the silicon-containing reactive group or those of the oxyalkylene base polymer having the silicon-containing reactive group, a composition comprising these two polymers is proposed (cf. U.S. Pat. Nos. 4,593,068 and U.S. patent application Ser. No. 246,102, filed Sep. 19, 1988 and now abandoned).
To adjust elongation or strength at break of the cured material of the composition comprising the above two polymers, it is possible to add a silicon-containing compound having a hydrolyzable group bonded to the silicon atom (cf. U.S. patent application Ser. No. 187,140 filed Apr. 28, 1988, now U.S. Pat. No. 4,910,255). The silicon-containing compound also serves for improving storage stability of the composition and prevents gelation or viscosity increase of the composition. However, the silicon-containing compound which can sufficiently improve the storage stability of the composition decreases the elongation of the cured material of the composition. Accordingly, when the decrease of elongation of the cured material is undesirable, it is difficult to provide a composition having good storage stability.